Method and system for providing an uplink structure and minimizing pilot signal overhead in a wireless communication network

ABSTRACT

An uplink control structure and pilot signal having minimal signal overhead for providing channel estimation and data demodulation in a wireless communication network are presented. The uplink control structure enables mobile terminals to communicate with base stations to perform various functions including obtaining initial system access, submitting a bandwidth request, triggering a continuation of negotiated service, or providing a proposed allocation re-configuration header. A dedicated random access channel is provided to communicatively couple the base station and mobile terminal allowing the mobile terminal to select a random access signaling identification. A resource request is received at the base station to uplink resource information from the mobile terminal and an initial access information request is received from the mobile terminal to configure the base station connection. Pilot signals with varying density configurations are provided, including low density symbol patterns for multiple contiguous resource blocks and high density symbol patterns for single resource blocks.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 12/989,044, entitled “Method and System forProviding an Uplink Structure and Minimizing Pilot Signal Overhead in aWireless Communication Network”, filed Jun. 21, 2011, now issued as U.S.Pat. No. 8,761,115, which is a submission under 35 U.S.C. 371 for U.S.National Stage Patent Application of International Application NumberPCT/CA2009/000523, filed Apr. 21, 2009, which claims priority to U.S.Provisional Application No. 61/046,596, filed Apr. 21, 2008 and U.S.Provisional Application No. 61/050,303, filed May 5, 2008. All of theabove-named applications are hereby incorporated by reference in theirentireties as though fully and completely set forth herein.

FIELD OF THE INVENTION

The present invention relates to the field of wireless communicationsand more particularly to a method and system for providing an uplinkcontrol structure and a pilot signal that utilizes minimum overhead toprovide channel estimation and data demodulation in the wirelesscommunication network.

BACKGROUND OF THE INVENTION

Wireless communication networks, such as cellular networks, operate bysharing resources among the mobile terminals operating in thecommunication network. As part of the sharing process, one or morecontrolling devices allocate system resources relating to channels,codes, among other resources. Certain types of wireless communicationnetworks, e.g., orthogonal frequency division multiplexed (“OFDM”)networks, are used to support cell-based high speed services such asthose under the IEEE 802.16 standards. The IEEE 802.16 standards areoften referred to as WiMAX or less commonly as WirelessMAN or the AirInterface Standard.

OFDM technology uses a channelized approach and divides a wirelesscommunication channel into many sub-channels which can be used bymultiple mobile terminals at, the same time. These sub-channels can besubject to interference, which may cause data loss.

A system and method are needed for providing an uplink control structureand a pilot signal for obtaining channel information during uplinkoperations from the mobile terminals to the base station using minimumsignal overhead. Existing systems do not employ uplink controlstructures. To the extent that pilot symbols are provided, the pilotsymbols are arranged in a fixed pattern that is predefined forpreselected resource block sizes. A system and method are proposed belowthat provide an uplink control structure and an efficient pilot signalhaving adaptive density and allocation design and which are scalable fordifferent size resource blocks.

SUMMARY OF THE INVENTION

The invention advantageously provides a method and system for providingan uplink control structure and a pilot signal that utilizes minimumoverhead to provide channel estimation and data demodulation in thewireless communication network.

A method is provided for uplink control in a wireless communicationnetwork, wherein the wireless communication network includes at leastone base station that is communicatively coupled to at least one mobileterminal. A dedicated random access channel is provided tocommunicatively couple the base station and the mobile terminal so thatthe mobile terminal can select a random access signaling identification.A resource request is received at the base station to uplink resourceinformation from the mobile terminal and an initial access informationrequest is received from the mobile terminal to configure the basestation connection.

The invention also provides a method of generating a low density pilotsymbol pattern. A first resource block is provided having a first axisthat defines a time domain and a second axis that defines a frequencydomain, the first resource block having a predefined pilot symbolpattern, including boundary pilot symbols. A second resource block isprovided having a third axis that defines a time domain and a fourthaxis that defines a frequency domain; replicating the predefined pilotsymbol pattern from the first resource block to the second resourceblock. The first resource block and the second resource block areconcatenated to establish a first boundary line between the firstresource block and the second resource block. Boundary pilot symbols aremaintained in a first area of the first resource block, wherein thefirst area is positioned along the first axis at an end opposite to thefirst boundary line. The boundary pilot symbols are maintained in asecond area of the second resource block, wherein the second area ispositioned along the fourth axis at an end opposite to the firstboundary line. Pilot symbols are deleted at the boundary between thefirst resource block and the second resource block adjacent to the firstboundary line and spacing of the remaining pilot symbols is adjustedbetween the first area and the second area to provide uniform spreadingof the pilot symbols.

The invention also provides a method of generating a high density pilotsymbol pattern. A concatenated structure is provided that includes afirst resource block having a first axis that defines a time domain anda second axis that defines a frequency domain, a second resource blockhaving a third axis that defines a time domain and a fourth axis thatdefines a frequency domain, and a third resource block having a fifthaxis that defines a time domain and a sixth axis that defines afrequency domain, wherein a first boundary line is established betweenthe first resource block and the second resource block and a secondboundary line is established between the second resource block and thethird resource block. A predefined pilot symbol pattern is providedwithin the concatenated structure, the predefined pilot symbol patternincludes first boundary pilot symbols provided in a first area of thefirst resource block that is positioned along the first axis at an endopposite to the first boundary line and second boundary pilot symbolsprovided in a second area of the third resource block that is positionedalong the fifth axis at an end opposite to the second boundary line. Thethird resource block is deleted. Third boundary pilot symbols areprovided in a third area of the second resource block that is positionedalong the third axis at an end opposite the first boundary line andspacing of the pilot symbols is adjusted between the first area and thethird area to provide uniform spreading of the pilot symbols.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, and theattendant advantages and features thereof, will be more readilyunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 is a block diagram of an exemplary cellular communication systemconstructed in accordance with the principles of the present invention;

FIG. 2 is a Hock diagram of an exemplary base station constructed inaccordance with the principles of the present invention;

FIG. 3 is a block diagram of an exemplary mobile terminal constructed inaccordance with the principles of the present invention;

FIG. 4 is a block diagram of an exemplary relay station constructed inaccordance with the principles of the present invention;

FIG. 5 is a block diagram of a logical breakdown of an exemplary OFDMtransmitter architecture constructed in accordance with the principlesof the present invention;

FIG. 6 is a block diagram of a logical breakdown of an exemplary OFDMreceiver architecture constructed in accordance with the principles ofthe present invention;

FIG. 7 illustrates resource blocks having uplink pilot designs for twotransmitter systems in accordance with the principles of the presentinvention;

FIG. 8 illustrates resource blocks having uplink pilot designs for fourtransmitter systems in accordance with the principles of the presentinvention;

FIG. 9 illustrates a flow diagram of the mobile terminal access anduplink resource allocation in accordance with the principles of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

As an initial matter, while certain embodiments are discussed in thecontext of wireless networks operating in accordance with the IEEE802.16 broadband wireless standard, which is hereby incorporated byreference, the invention is not limited in this regard and may beapplicable to other broadband networks including those operating inaccordance with other OFDM orthogonal frequency division (“OFDM”)-basedsystems, including the 3rd Generation Partnership Project (“3GPP”) and3GPP2 evolutions. Similarly, the present invention is not limited solelyto OFDM-based systems and can be implemented in accordance with othersystem technologies, e.g., CDMA.

Referring now to the drawing figures in which like reference designatorsrefer to like elements, there is shown in FIG. 1, an exemplarycommunication system 10 is provided in accordance with the principles ofthe present invention. Communication system 10 includes a base stationcontroller (“BSC”) 12 which controls wireless communications withinmultiple cells 14, which cells are served by corresponding base stations(“BS”) 16. In some configurations, each cell is further divided intomultiple sectors 18 or zones (not shown). In general, each base station16 facilitates communications using orthogonal frequency divisionmultiplexing (“OFDM”) with mobile and/or mobile terminals 20, which arewithin the cell 14 associated with the corresponding base station 16.The movement of the mobile terminals 20 in relation to the base stations16 results in significant fluctuation in channel conditions. Asillustrated, the base stations 16 and mobile terminals 20 may includemultiple antennas to provide spatial diversity for communications. Insome configurations, relay stations 22 may assist in communicationsbetween base stations 16 and mobile terminals 20. Mobile terminals 20can be handed off from any cell 14, sector 18, zone (not shown), basestation 16 or relay 22 to another cell 14, sector 18, zone (not shown),base station 16 or relay 22. In some configurations, base stations 16communicate with each other and with another network (such as a corenetwork or the Internet, both not shown) over a backhaul network 24. Insome configurations, a base station controller 12 is not needed.

With reference, to FIG. 2, an example of a base station 16 isillustrated. The base station 16 generally includes a base controlsystem 26, e.g. a CPU, a baseband processor 28, transmit circuitry 30,receive circuitry 32, multiple antennas 34 a, 345 and a networkinterface 36. The receive circuitry 32 receives radio frequency signalsbearing information through a receive antenna 34 a from one or moreremote transmitters provided by mobile terminals 20 (illustrated in FIG.3) and relay stations 22 (illustrated in FIG. 4). A low noise amplifierand a filter (not shown) may cooperate to amplify and remove broadbandinterference from the signal for processing. Down-conversion anddigitization circuitry (not shown) down-convert the filtered, receivedsignal to an intermediate or baseband frequency signal, which isdigitized into one or more digital streams.

The baseband processor 28 processes the digitized received signal toextract the information or data bits conveyed in the received, signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. As such, the baseband processor 28 is generallyimplemented in one or more digital signal processors (“DSPs”) and/orapplication-specific integrated circuits (“ASICs”). The receivedinformation is sent across a wireless network via the network interface36 or transmitted to another mobile terminal 20 serviced by the basestation 16, either directly or with the assistance of a relay 22.

On the transmit side, the baseband processor 28 receives digitized data,which may represent voice, data, or control information, from thenetwork interface 36 under the control of the base control system 26,and encodes the data for transmission. The encoded data is output to thetransmit circuitry 30, where it is modulated by one or more carriersignals having a desired transmit frequency or frequencies. A poweramplifier (not shown) amplifies the modulated carrier signals to a levelappropriate for transmission, and delivers the modulated carrier signalsto the transmit antennas 34 b through a matching network (not shown).Modulation and processing details are described in greater detail below.

With reference to FIG. 3, an example of a mobile terminal 20 isillustrated. Similarly to the base station 16, the mobile terminal 20includes a mobile control system 38, e.g. a CPU, a baseband processor40, transmit circuitry 42, receive circuitry 44, multiple antennas 46 a,46 b and user interface circuitry 48. The receive circuitry 44 receivesradio frequency signals bearing information through a receive antenna 46a from one or more base stations 16 and relays 22. A low noise amplifierand a filter (not shown) may cooperate to amplify and remove broadbandinterference from the signal for processing. Down-conversion anddigitization circuitry (not shown) down-convert the filtered, receivedsignal to an intermediate or baseband frequency signal, which isdigitized into one or more digital streams.

The baseband processor 40 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. The baseband processor 40 is generallyimplemented in one or more DSPs and/or ASICs.

For transmission, the baseband processor 40 receives digitized data,which may represent voice, video, data, or control information, from themobile control system 38, which it encodes for transmission. The encodeddata is output to the transmit circuitry 42, where it is used by amodulator to modulate one or more carrier signals at a desired transmitfrequency or frequencies. A power amplifier (not shown) amplifies themodulated carrier signals to a level appropriate for transmission, anddelivers the modulated carrier signal to the transmit antennas 46 hthrough a matching network (not shown). Various modulation andprocessing techniques available to those skilled in the art are used forsignal transmission between the mobile terminal and the base station,either directly or via the relay station.

In OFDM modulation, the transmission band is divided into multiple,orthogonal carrier waves. Each carrier wave is modulated according tothe digital data to be transmitted. Because OFDM divides thetransmission band into multiple carriers, the bandwidth per carrierdecreases and the modulation time per carrier increases. Since themultiple carriers are transmitted in parallel, the transmission rate forthe digital data, or symbols, on any given carrier is lower than when asingle carrier is used.

OFDM modulation utilizes the performance of an Inverse Fast FourierTransform (“IFFT”) on the information to be transmitted. Fordemodulation, the performance of a Fast Fourier Transform (“FFT”) on thereceived signal recovers the transmitted information. In practice, theIFFT and FFT are provided by digital signal processing carrying out anInverse Discrete Fourier Transform (“IDFT”) and Discrete FourierTransform (“DFT”), respectively. Accordingly, the characterizing featureof OFDM modulation is that orthogonal carrier waves are generated formultiple bands within a transmission channel. The modulated signals aredigital signals having a relatively low transmission rate and capable ofstaying within their respective bands. The individual carrier waves arenot modulated directly by the digital signals. Instead, all carrierwaves are modulated at once by IFFT processing.

In operation, OFDM is preferably used for at least downlink transmissionfrom the base stations 16 to the mobile terminals 20. Each base station16 is equipped with “n” transmit antennas 34 b (n>=1), and each mobileterminal 20 is equipped with “m” receive antennas 46 a (m>=1). Notably,the respective antennas can be used for reception and transmission usingappropriate duplexers or switches and are so labeled only for clarity.

When relay stations 22 are used, OFDM is preferably used for downlinktransmission from the base stations 16 to the relays 22 and from relaystations 22 to the mobile terminals 20.

With reference to FIG. 4, an example of a relay station 22 isillustrated. Similarly to the base station 16, and the mobile terminal20, the relay station 22 includes a relay control system 50, e.g. a CPU,a baseband processor 52, transmit circuitry 54, receive circuitry 56,multiple antennas 58 a, 58 b and relay circuitry 60. The relay circuitry60 enables the relay 22 to assist in communications between a basestation 16 and mobile terminals 20. The receive circuitry 56 receivesradio frequency signals bearing information through a receive antenna 58a from one or more base stations 16 and mobile terminals 20. A low noiseamplifier and a filter (not shown) may cooperate to amplify and removebroadband interference from the signal for processing. Down-conversionand digitization circuitry (not shown) down-convert the filtered,received signal to an intermediate or baseband frequency signal, whichis digitized into one or more digital streams.

The baseband processor 52 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. The baseband processor 52 is generallyimplemented in one or more DSPs and/or ASICs.

For transmission, the baseband processor 52 receives digitized data,which may represent voice, video, data, or control information, from therelay control system 50, which it encodes for transmission. The encodeddata is output to the transmit circuitry 54, where it is used by amodulator to modulate one or more carrier signals that is at a desiredtransmit frequency or frequencies. A power amplifier (not shown) willamplify the modulated carrier signals to a level appropriate fortransmission, and deliver the modulated carrier signal to the transmitantenna 58 b through a matching network (not shown). Various modulationand processing technique; available to those skilled in the art are usedfor signal transmission between the mobile terminal 20 and the basestation 16, either directly or indirectly via a relay station 22, asdescribed above.

With reference to FIG. 5, a logical OFDM transmission architecture isprovided, the base station controller 12 (See FIG. 1) sends datadestined for transmission to various mobile terminals 20 to the basestation 16, either directly or with the assistance of the relay station22. The base station 16 may use channel quality indicators (“CQIs”)associated with the mobile terminals 20 to schedule the data fortransmission as well as select appropriate coding and modulation fortransmitting the scheduled data. The CQIs may be obtained directly fromthe mobile terminals 20 or may be determined at the base station 16using information provided by the mobile terminals 20. In either case,the CQI for each mobile terminal 20 is a function of the degree to whichthe channel amplitude (or response) varies across the OFDM frequencyband.

The scheduled data 62, which is a stream of bits, is scrambled in amanner that reduces the peak-to-average power ratio associated with thedata using data scrambling logic 64. A cyclic redundancy check (“CRC”)for the scrambled data is determined and appended to the scrambled datausing CRC, adding logic 66. Channel coding is performed using channelencoder logic 68 to effectively add redundancy to the data to facilitaterecovery and error correction at the mobile terminal 20. Again, thechannel coding for a particular mobile terminal 20 is based on the CQI.In some implementations, the channel encoder logic 68 uses known Turboencoding techniques. The encoded data is processed by rate matchinglogic 70 to compensate for the data expansion associated with encoding.

The bit interleaver logic 72 systematically reorders the bits in theencoded data to minimize the loss of consecutive data bits. Theresultant data bits are systematically mapped into corresponding symbolsdepending on the chosen baseband modulation by mapping logic 74.Preferably, Quadrature Amplitude Modulation (“QAM”) or Quadrature PhaseShift Key (“QPSK”) modulation is used. The degree of modulation ispreferably chosen based on the CQI for the particular mobile terminal20. The symbols may be systematically reordered to further bolster theimmunity of the transmitted signal to periodic data loss caused byfrequency selective fading using symbol interleaver logic 76.

At this point, groups of bits are mapped into symbols representinglocations in an amplitude and phase constellation. When spatialdiversity is desired, blocks of symbols are processed by space-timeblock code (“STC”) encoder logic 78, which modifies the symbols in afashion making the transmitted signals more resistant to interferenceand more readily decoded at the mobile terminal 20. The STC encoderlogic 78 processes the incoming symbols and provide “n” outputscorresponding to the number of transmit antennas 34 b for the basestation 16. The base control system 26 and/or baseband processor 28, asdescribed above with respect to FIG. 2, provide a mapping control signalto control STC encoding. At this point, assume the symbols for the “n”outputs are representative of the data to be transmitted and are capableof being recovered by the mobile terminal 20.

For the present example, assume the base station 16 has two transmitantennas 32 b (n=2) and the STC encoder logic 78 provides two outputstreams of symbols. Accordingly, each of the symbol streams that areoutput by the STC encoder logic 78 is sent to a corresponding IFFTprocessor 80 a, 80 b (referred to collectively herein as IFFT 80),illustrated separately for ease of understanding. Those skilled in theart will recognize that one or more processors may be used to providesuch digital signal processing, alone or in combination with otherprocessing described herein. The IFFT processors 80 preferably operateon the respective symbols to provide an inverse Fourier Transform. Theoutput of the IFFT processors 80 provides symbols in the time domain.The time domain symbols are grouped into frames, which are associatedwith a prefix-by-prefix insertion logic 82 a, 82 b (referred tocollectively herein as prefix insertion 82). Each of the resultantsignals is up-converted in the digital domain to an intermediatefrequency and converted to an analog signal via the correspondingdigital up-conversion (“DUC”) and digital-to-analog (“D/A”) conversioncircuitry 84 a, 84 b (referred to collectively herein as DUC+D/A 84).The resultant (analog) signals are simultaneously modulated at thedesired RF frequency, amplified, and transmitted via the RF circuitry 86a, 86 b (referred to collectively herein as RE circuitry 86) andantennas 34 b. Notably, pilot signals known by the intended mobileterminal 16 are scattered among the sub-carriers. The mobile terminal16, which is discussed in detail below, uses the pilot signals forchannel estimation.

Reference is now made to FIG. 6 to illustrate reception of thetransmitted signals by a mobile terminal 20, either directly from basestation 16 or with the assistance of relay 22. Upon arrival of thetransmitted signals at each of the antennas 46 a of the mobile terminal20, the respective signals are demodulated and amplified bycorresponding RF circuitry 88. For the sake of conciseness and clarity,only one of the two receive paths is described and illustrated indetail. Analog-to-digital (A/D) converter and down-conversion circuitry90 digitizes and down-converts the analog signal for digital processing.The resultant digitized signal may be used by automatic gain controlcircuitry (AGC) 92 to control the gain of the amplifiers in the RFcircuitry 88 based on the received signal level.

Initially, the digitized signal is provided to synchronization logic 94,which includes coarse synchronization logic 96, which buffers severalOFDM symbols and calculates an auto-correlation between the twosuccessive OFDM symbols. A resultant time index corresponding to themaximum of the correlation result determines a fine synchronizationsearch window, which is used by fine synchronization logic 98 todetermine a precise framing starting position based on the headers. Theoutput of the fine synchronization logic 98 facilitates frameacquisition by frame alignment logic 100. Proper framing alignment isimportant so that subsequent FFT processing provides an accurateconversion from the time domain to the frequency domain. The finesynchronization algorithm is based on the correlation between thereceived pilot signals carried by the headers and a local copy of theknown pilot data. Once frame alignment acquisition occurs, the prefix ofthe OFDM symbol is removed with prefix removal logic 102 and resultantsamples are sent to frequency offset correction logic 104, whichcompensates for the system frequency offset caused by the unmatchedlocal oscillators in the transmitter and the receiver. Preferably, thesynchronization logic 94 includes frequency offset and clock estimationlogic 106, which is based on the headers to help estimate such effectson the transmitted signal and provide those estimations to thecorrection logic 104 to properly process OFDM symbols.

At this point, the OFDM symbols in the time domain are ready forconversion to the frequency domain using FFT processing logic 108. Theresults are frequency domain symbols, which are sent to processing logic110. The processing logic 110 extracts the scattered pilot signal usingscattered pilot extraction logic 112, determines a channel estimatebased on the extracted pilot signal using channel estimation logic 114,and provides channel responses for all sub-carriers using channelreconstruction logic 116. In order to determine a channel response foreach of the sub-carriers, the pilot signal is essentially multiple pilotsymbols that are scattered among the data symbols throughout the OFDMsub-carriers in a known pattern in both time and frequency.

FIGS. 7 and 8 illustrate resource blocks (“RBs”) 70, 70 a-70 n, 80, 80a-80 n (hereinafter “RB 70,80”) having uplink pilot designs. The RB70,80 include pilot symbols arranged in patterns according toembodiments of the invention. An RB is defined as a smallest unit forchannelization and is used mostly for small packet transmission (VoIP).The RB may be configured in various sizes such as 12×6, 18×6, and 6×4,among other sizes. A basic channel unit (BCU) is the smallest unit ofassignment for channelization. The pilot symbol patterns are arranged inthe RB 70,80 to include a boundary pilot pattern and an adaptive densityand allocation pattern. The RB 70,80 includes a horizontal axis thatrepresents time and a vertical axis that represents frequency. The pilotsymbol patterns are employed for channel estimation, data demodulation,and sounding, among other purposes. The pilot symbol patterns for acontiguous resource region may include a scattered pilot symbol patternand pilot symbols allocated at boundaries of the resource region.

FIGS. 7 and 8 illustrate multiple RB configurations having pilot symbolpatterns with different density configurations for a two transmittersystem and a four transmitter system, respectively. The pilot symboldensity and pilot symbol pattern may be configured in time and frequencyto accommodate different contiguous resource sizes. The pilot symbol forthe first transmitter is identified by “1,” the pilot symbol for thesecond transmitter is identified by “2,” the pilot symbol for the thirdtransmitter is identified by “3,” the pilot symbol for the fourthtransmitter is identified by “4.” The RB 70,80 includes areas for pilotsymbols and areas for data signals. The invention seeks to reduce RB70,80 overhead by maximizing area (e.g., resources) for data signals andreducing area for pilot symbols. Additionally, the uplink pilot designfor a diversity zone and a localized zone may be unified by designingpilot structures based on adaptive density and allocation. Pilot symbolpatterns having different density values may be generated for differentnumbers of contiguous RBs 70,80. The pilot symbol pattern and densityvalue may be chosen based on the size of the contiguous resource and amulti-antenna transmission and reception (MIMO) mode.

According to embodiments illustrated in FIGS. 7 and 8, pilot symbolpatterns may be generated with different density values for multiplecontiguous RBs 70,80. A stand alone RB 70,80 having a high density pilotsymbol pattern may be coupled with other RBs 70,80 to provide a lowdensity pilot symbol pattern. The pilot symbol pattern for a stand aloneRB 70,80 may include pilot symbols allocated on the boundary to form ahighest density pilot symbol pattern. The stand alone RB pilot patternmay be extended to a pilot pattern for two RBs 70,80, which provides alower density pilot symbol pattern. The two stand alone. RBs 70,80 maybe concatenated, either in frequency or in time. In order to reducepilot, symbol pattern, density, redundant pilot symbols may beeliminated at the boundary between two RBs 70,80. The spacing of thepilot symbols may be adjusted in frequency and/or in time to provideuniform spreading of pilot symbols. This method may be used to extend,pilot symbol patterns to multiple RBs 70,80. As the number of contiguousRBs 70,80 increase, the pilot symbol density pattern for the RBs 70,80may change from a high density pattern to a low density pattern. Thetotal pilot symbol spacing may be adjusted in the frequency and timedirections to remain smaller than pre-defined maximum values.

According to an alternative embodiment, a number of contiguous RBs 70,80may be provided that collectively include a low density pilot symbolpattern. In this case, the contiguous RBs 70,80 may be transformed to astand alone. RB 70,80 having a high density pilot symbol pattern. Pilotsymbols may be uniformly allocated in frequency and time, with maximumpilot spacing provided for N RBs (usually N>3). Boundary pilot symbolsmay be allocated in time and frequency to minimize extrapolation. The NRBs 70,80 may be reduced to N−1 RBs 70,80 by maintaining a pilot symbolpattern having boundary pilot symbols. Pilot symbol spacing may beadjusted to uniformly spread the pilot symbols in the time and frequencydirections. In this case, the pilot symbol density for the RBs 70,80 maychange from low density pattern to a high density pattern. This processmay continue until single RB 70,80 remains having a high pilot symboldensity.

FIGS. 7 and 8 illustrate several pilot symbol density patterns. A lowdensity pilot symbol pattern (3.1%<density<5.3% for one transmitter) maybe realized for more than one contiguous BCU, more than 3 contiguousRBs, or for more than one sub frame. A medium density pilot symbolpattern (density {tilde over ( )}5.6% for one transmitter) may berealized for one BCU or 3 contiguous RBs. A high density pilot symbolpattern (6.3%<density<8.3%) may be realized for less than 3 RBs. Thehigh density pilot symbol pattern may be used, for example, for VoIPtransmission. The invention enables the pilot symbol pattern to adjustin time and frequency based on the size of contiguous RBs 70,80.

Referring again to FIG. 6, the processing logic 110 compares thereceived pilot symbols with the expected pilot symbols in certainsub-carriers at certain times to determine a channel response for thesub-carriers in which pilot symbols were transmitted. The results may beinterpolated to estimate a channel response for the remainingsub-carriers for which pilot symbols are not provided. The actual andinterpolated channel responses may be used, to estimate an overallchannel response, which includes the channel responses for thesub-carriers in the OFDM channel.

The frequency domain symbols and channel reconstruction information,which are derived from the channel responses for each receive path areprovided to an STC decoder 118, which provides STC decoding on bothreceived paths to recover the transmitted symbols. The channelreconstruction information provides equalization information to the STCdecoder 118 sufficient to remove the effects of the transmission channelwhen processing the respective frequency domain symbols.

The recovered symbols are placed back in order using symbolde-interleaver logic 120, which corresponds to the symbol interleaverlogic 76 of the base station 16 transmitter. The de-interleaved symbolsare then demodulated or de-mapped to a corresponding bit stream using demapping logic 122. The bits are then de-interleaved using bitde-interleaver logic 124, which corresponds to the bit interleaver logic72 of the base station 16 transmitter architecture. The de-interleavedbits are then processed by rate de-matching logic 126 and presented tochannel decoder logic 128 to recover the initially scrambled data andthe CRC checksum. Accordingly, the CRC logic 130 removes the CRCchecksum, checks the scrambled data in traditional fashion, and providesit to the de-scrambling logic 132 for descrambling using the known basestation de-scrambling code to recover the originally transmitted data134.

While recovering the data 134, a CQI 136 or at least informationsufficient to create a CQI at the base station 16 is determined bychannel variation analysis logic 138 and transmitted to the base station16. As noted, above, the CQI 134 may be a function of thecarrier-to-interference ratio (“CIR”) 140, as well as the degree towhich the channel response varies across the various sub-carriers in theOFDM frequency band. For this embodiment, the channel gain for eachsub-carrier in the OFDM frequency band used to transmit information iscompared relative to one another to determine the degree to which thechannel gain varies across the OFDM frequency hand. Although numeroustechniques are available to measure the degree of variation, onetechnique is to calculate the standard deviation of the channel gain foreach sub-carrier throughout the OFDM frequency band being used totransmit data.

According to one embodiment, the invention provides an uplink controlstructure for OFDM systems that enables mobile terminals 20 tocommunicate with the base stations 16. The control structure includes anuplink acknowledge (UL ACK) channel and a dedicated control channel thatfeeds information back, such as channel quality indicator (CQI)information, pre-coding matrix index (PMI) information and rankinformation, among other information. According to one embodiment, themobile terminals 20 may employ the UL ACK channel for initial access tothe OFDM system, for bandwidth requests, to trigger continuation ofnegotiated service, and for proposed allocation of a re-configurationheader, among other purposes.

A fixed number of resources may be allocated for the UL ACK channels. Aset of ACK channels is defined for all unicast assignments and aseparate set of ACK channels is defined for group assignments. The ACKchannels that are used for a given packet transmission are determined bythe partition number and the layer. The ACK signals are transmitted overseveral ACK tiles, where an ACK tile is defined as a group of contiguoustones or sub-carriers. The value of the ACK signals may be determined byeither non-coherent detection or coherent detection. An orthogonalspreading code may be used to multiplex multiple ACK signals on to thesame ACK tile.

An uplink (“UL”) control channel structure supports UL ACK channels forboth unicast assignments and group assignments. The UL control channelstructure also supports multiple ACKs for different packets that aretransmitted on the same resources, as in multi-codeword MIMO(“MCW-MIMO”) or multi-user MIMO (“MU-MIMO”). The UL control channel alsoprovides feedback for frequency selective scheduling and pre-coding,including for simple diversity assignments.

A fixed number of resources may be allocated for the UL dedicatedcontrol channel. The resources are divided into UL control tiles,wherein the number of tiles allocated to a user depends on the amount offeedback requested. The allocated tiles may be spread over the band toobtain frequency diversity. The UL control information is CRC protectedand is scrambled by the user ID. The content of the information canchange each feedback instance to accommodate event driven controlinformation such as a bandwidth request.

A UL random access (“RA”) channel may be provided to enable the user toinitially gain access to the system through one of several physicalcontrol structures. According to one embodiment, the UI, random accesschannel is a designated resource. The UL random access channel may be acontention based channel for multiple mobile terminals 20 to requestaccess/bandwidth. A designated resource may be allocated for theseaccess requests. The access request may be spread or repeated across theresources that are used exclusively for random access and bandwidthrequests. The mobile station 20 may randomly select, from one sequenceand location if multiple possibilities are available.

According to one embodiment, the mobile terminal 20 may randomly selectfrom one of L sequences, which spans N RBs 70,80. Alternatively, thesequence length L may be chosen to confine a full sequence within an RB70,80. By confining the spreading sequence to one RB 70,80, thespreading sequences maintain orthogonality as the RB 70,80 is virtuallyfrequency flat as the RB contains physical contiguous tones. Thespreading sequences may be repeated in each RB 70,80 to gain diversity.

If many resources are assigned for uplink control, the resources may bedivided into TO time-frequency blocks fix random access. In this case,the number of distinct codes/resource per sub frame is LM, where thevalue of M may be dynamically specified by the base station 16. In someembodiments, a sub-frame within a superframe (or otherwise specified asset of F frames) is also randomly selected, wherein the number ofdistinct codes/resource/sub frames per superframe is defined as LMF.

Another physical control structure includes overlaying the random accessrequests with UL control signals. The access request may be spread orrepeated across the resources used for uplink control, such as CQI,among other uplink control. The mobile terminal 20 may randomly selectfrom one sequence and location if multiple possibilities are available.For example, the mobile terminal 20 may randomly select from one of Lsequences, where L is less than or equal to the RB size. By confiningthe spreading sequence to one RB 70,80, the spreading sequences maintainorthogonality as the RB 70,80 is virtually frequency flat as the RB70,80 includes physical contiguous tones or sub-carriers. The length-Lsequence is completely repeated on each of the N RBs 70,80. Coherentcombining of each sequence repetition may improve detection at the basestation 16.

While overlaying the RA request and UL signals, the resources may bedivided into M time-frequency blocks for random access if many resourcesare assigned for uplink control. A number of distinct codes or resourcesper sub-frame is LM. The values of N and M may be dynamically specifiedby the base station 16. In some embodiments, a sub-frame within thesuperframe (or otherwise specified as a set of frames) is also randomlyselected. In some embodiments, the sequences span the N RBs 70,80. Thesequence length in these cases is LN and the number of distinct codes orresource per sub frame is LNM.

In some embodiments, the L sequences are an orthogonal set of spreadingsequences, wherein the L-sequences may be divided into two types ofindications. A first type includes a system access request without apreviously assigned mobile terminal ID and a second type includes asystem access request with an assigned mobile terminal ID. If a mobileterminal 20 is provided access to the system, a down link (DL) controlsegment access grant may be scrambled by the sequence/resource block ID.The base station 16 may attempt interference cancellation to remove theRA channel from UL control.

Another physical control structure includes overlaying the RA channelover the wideband UL resources. The request is spread or repeated acrossthe UL channel, possibly across the en tire bandwidth. The random accessoperation for users may be assigned to one length L sequence and onelocation, if multiple possibilities are available.

A random access channel may be assigned one length L sequence for use byall users. The total resources NT may be divided into M time-frequencyblocks for random access. The access sequence, through spreading andrepetition, may span NT/M=N RB's (e.g. N=3). The mobile terminal 20randomly selects one of the M, wherein the number of distinctionresource per sub frame is M. The sub frame for a request is alsorandomly selected.

The sequences for random access may be an orthogonal set of spreadingsequences. Two sequences may be defined for two types of indications. Afirst type includes a system access request without a previouslyassigned mobile terminal ID and a second type includes a system accessrequest with an assigned mobile terminal ID. If a mobile terminal 20 isprovided access to the system, a down link (DL) control segment accessgrant may be scrambled by the sequence/resource block ED. The basestation 16 may attempt interference cancellation to remove the RAchannel from UL control. The base station 16 may try decoding UL controland traffic transmissions with and without an assumption that an RA wassent.

Once a mobile terminal 20 accesses the system, the mobile terminal 20may request resources on the UL to transmit information to the basestation 16. The invention provides the mobile terminal 20 with severaloptions for performing the UL resource request. Parameters for a firsttransmission may be specified by a bandwidth request, the parameters maybe set to default based on capability negotiation, the parameters may beset to a previous configuration based on renewal, or the parameters maybe set in some other manner. The mobile terminal 20 may change theassignment parameters by including an additional re-configurationmessage encoded with data that takes effect eat the start of the nextpacket transmission. This takes advantage of HAW for the controlmessage.

According to one embodiment, a field may be appended to a data packetprior to encoding. After the data packet is decoded at the base station16, the header is located to determine if an additional re-configurationmessage has be added to the packet with re-configuration information.Header operations may include a 2-bit header field that indicates thepresence and type of service re-configuration message. For example, ‘00’may indicate no change to a configuration and no re-configurationmessage; ‘01’ may indicate no change to a configuration, nore-configuration message, and extend service for another packet; ‘10’may indicate that a re-configuration message of Type 1 is attached; and‘11’ may indicate that a re-configuration message of Type 2 is attached.

A re-configuration message may include changes to an exiting assignmentor to future assignments, including mobile power header room, update ofcapabilities, request for different MIMO mode, request for different MCSindication of mobile data backlog size, indication to continue assigningUL resources until data backlog is emptied, resource size specification,delay requirement, quality of service (“QoS”), and requests of anadditional service/resources, among other transmission parameters.

The mobile terminal 20 may randomly select an RA signaling ID. Asignaling ID may be a specific spreading sequence, a time-frequencylocation, a time slot, an interlace, or other signaling ID. The set ofsignaling ID options are known to users and also the index associatedwith each signaling ID option.

In response to a random access channel signal, the base station 16 mayassign one or more of a user ID to the user, an initial UL resource forthe mobile to provide information, user equipment capabilities, a DLresource assignment requesting information from the mobile terminal andadditional details, such as group assignment, base station procedures,among other parameters. The assignment message may carry user IDinformation.

A message sent to the mobile terminal 20 from the base station 16 mayidentify the base station 16 using a randomly selected signaling IDoption that is selected by the user for the RA. For example, if thecontrol channels are generally scrambled in some manner by the user IDin response to a RA, the base station 16 will send a control messagescrambled by the index of the randomly selected signaling ID, such assequence index, sequence location, etc.

In another embodiment, some signaling may be reserved for users thathave been assigned user IDs. For example, a user may be in a hand-offoperation and may be accessing a new serving sector. A user may selectfrom a set of random access signaling IDs if an assigned user ID is notprovided. Alternatively, a user may select from a different subset ofsignaling options if the user does have a user ID. In response, the basestation 16 may send a control message that is scrambled by the RA signalindex and includes a user ID if the mobile terminal 20 has sent asignaling option indicating a user ID is not provided. Alternatively, ifthe mobile has sent a signaling option indicating it does have a userID, then the base station 16 may send a control message that isscrambled by the RA signal index without a user ID. The mobile terminal20 may indicate the user ID in the next transmission for user equipmentcapabilities, etc.

According to one embodiment, the header and optionally a message bodymay be added to a first packet transmission. Alternatively, the headerand optionally a message body may be added to a first packettransmission and every Nth packet afterwards, where N can be from 1 toinfinity. The base station 16 may provide the mobile terminal 20 with aACK/NAK of packet transmission to indicate that a re-configurationmessage was correctly received.

During an assignment of the mobile terminal 20, users may embed a headeron a data packet transmission that provides details on configuration orre-configuration. The request by the mobile terminal 20 for UL resourcesmay be made on dedicated resources within UL control tiles. Theseresource sizes may be different for different frames according to apre-determined pattern. The sizes may be known at the mobile terminal 20and the base station 16, so signaling is not needed after configuration.

According to one embodiment, the resource request may occupy a fieldthat is reserved for another message (CQL, ACK/NAK, precoder index,etc). The presence of a request may be specified by the UL controlmessage type. The mobile terminal 20 may set this type to a messageconfiguration that includes space for a resource assignment. As aresult, the size of the message may not be changed from the specifiedsize for that sub frame. The presence of the request field may bedynamic, but may not affect the pre-determined size of the user's ULcontrol. A resource request may be encoded with other UL control data sothat resource requests may be reliably received.

The request may have multiple forms for a given system. In a firstembodiment, the resource request may be a single “on/off” indication.Details of an assignment may be given in a re-configuration message ormay be known from previous or default configurations. Alternatively, theresource request may be a message, where details of assignments areindicated, such as delay constraints, QoS, packet backlog, and resourcesize, among other assignments. Details of an assignment may be given ina re-configuration message or may be known from previous or defaultconfigurations. For example, resources may be specified by a secondarybroadcast channel, UL resources may be allocated across distributed RBblocks, bandwidth requests may be 4-10 bits indicating QoS and a firsttransmission spectral efficiency or a mobile terminal 20 buffer size, abandwidth request may occupy a field otherwise assigned for anotherpurpose, such as DL CQI feedback, or UL, resources may be encoded withother UL control data for users so that a bandwidth request may bereliably received.

According to an alternative embodiment, users may be assigned one of therandom access signaling IDs (e.g., channel sequences or location) afteraccessing a system. A resource request may use the same sequence orchannel configurations. As with the RA channel, users also may beassigned specific sub frames for resource request, opportunities. Theassigned signaling may a unique identifier for a user's resourcerequest. In a first example, a set of signaling IDs may be reserved forresource requests and may not be used for RA requests. The assignedsequence or location may be a unique identifier for a user's resourcerequest. A user may be assigned signaling IDs to identify a bandwidthrequest or a resource request. Alternatively, users may be assignedsignaling IDs from a full set of RA signaling IDs. The sequence may bescrambled by resource request ID to identify as BW or resource request.The assigned sequence, location, or scrambling may be a uniqueidentifier for a user's resource request. Users may be assigned multiplesignaled IDs for different configured services, such as and http trafficresource requests, among other configured services. If the user hasanother mechanism for obtaining resource requests and opportunities forresource requests are frequent, the user may not be assigned signalingfor transmitting resource requests in this manner.

According to yet another embodiment, a bandwidth or resource request mayuse resources that are specified persistently. One or more RBs andmultiple RBs may be distributed to provide diversity. A UL bandwidth orresource may be overlaid with other traffic on a same resource as atraffic signal or a control signal. If the user has another mechanismfor resource requests and opportunities for requests are frequent, theuser may not be assigned signaling for transmitting resource requests inthis manner. UL bandwidth and resource requests for the mobile terminal20 may include 4-10 bits, with an initial message containing limitedfields, such as QoS and a first transmission spectral efficiency or amobile terminal buffer size including CRC. The UL bandwidth requests andresource requests for a mobile terminal 20 are intended to be reliablesignaling with diversity, with interference cancellation used at thebase station 16. Users may be separated by locations of RBs, sub frame,and assigned sequences. Regarding sequences, each user may be assigned asequence block to use. In other embodiments, users may be assigned asame set of sequences to facilitate detection at the base station 16.Alternatively, orthogonal sequences such as Zadoff-Chu or Walshsequences may be used. The sequence length may be less than the lengthof the RB. If N RBs are assigned for each resource request channel, itmay be repeated over all RBs. Alternatively, the sequence may be spreadover all N RBs.

The mobile terminal 20 may send a request for service signal. Themessage size may be minimal as it indicates a renewal or continuation ofa configured service. According to a first option, the service may berenewed through a single message after the mobile terminal receives a ULassignment for a given type of service. The message may be a simpleON/OFF toggle to renewal service with previous or existing parameters.The message may be sent in a persistently assigned UL control resourcespace and the message type may indicate that the service renewal isbeing signaled. The mobile terminals 20 may be assigned multiplemessages to toggle multiple services, parameters of renewal for firsttransmission may be set to a default and a re-configuration signal infirst transmission may provide parameter changes.

Alternatively, a scrambled ID may be provided to the mobile terminal 20for UL renewal request. After the mobile terminal 20 receives a ULassignment for a given type of service, the service may be renewedthrough a single message. The message may be a simple ON/OFF toggle torenew service with previous or existing parameters. The message may besent using resource requests in random access space to renew service tolast configuration parameters. The mobile terminals 20 may be assignedmultiple messages to toggle multiple services. The parameters of renewalfor a first transmission may be set to a default.

FIG. 9 illustrates an access and uplink resource allocation flow diagrambetween the mobile terminals 20 and the base station 16. The mobileterminals 20 initiate an access request to the base station 16 using arandomly selected sequence (step S90). The base station 16 provides themobile terminals 20 with an access grant and an initial assignment (stepS92). The mobile terminals 20 receive an initial UL assignment with auser ID and resource allocations (UL and/or DL) (step S94). The mobileterminals 20 submit a UL bandwidth request to the base station 16 (stepS95). The base station 16 provides UL resource assignments (step S96).The mobile terminal 20 performs data transmission, includingre-configuration of service and continuation of service (step S97). Ifthe mobile terminal 20 is moved into a different cell, then a UL servicerenewal request may be sent to the base station (step S98).

The invention may be realized in hardware, software, or a combination ofhardware and software. Any kind of computing system, or other apparatusadapted for carrying out the methods described herein, is suited toperform the functions described herein.

A typical combination of hardware and software could be a computersystem having one or more processing elements and a computer programstored on a storage medium that, when loaded and executed, controls thecomputer system such that it carries out the methods described herein.The invention can also be embedded in a computer program product, whichcomprises all the features enabling the implementation of the methodsdescribed herein, and which, when loaded in a computing system is ableto carry out these methods. Storage medium refers to any volatile ornon-volatile storage device.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed herein above. In addition, unless mention was made above tothe contrary, it should be noted that all of the accompanying drawingsare not to scale. A variety of modifications and variations are possiblein light of the above teachings without departing from the scope andspirit of the invention, which is limited only by the following claims.

What is claimed is:
 1. A method of providing uplink control in awireless communication network, the method comprising: by a mobileterminal: receiving a communication from a base station over anorthogonal frequency division multiplexed (OFDM) wireless network,wherein the communication invokes selection of a reserved random accesssignaling identification by the mobile terminal; selecting the reservedrandom access signaling identification in response to said receiving;transmitting to the base station a resource request determined at leastin part based on the selected reserved random access signalingidentification; transmitting an initial access information request tothe base station to configure a base station connection; transmitting tothe base station a resource request for sending uplink resourceinformation; and transmitting a service renewal request to the basestation using the reserved random access signaling identification whenthe mobile terminal moves to a different cell.
 2. The method accordingto claim 1, wherein said selecting the reserved random access signalingidentification includes embedding a header on a packet transmissioncommunicated from the mobile terminal to the base station.
 3. The methodaccording to claim 2, wherein the header on the packet transmissionselects a sequence length from a single resource block.
 4. The methodaccording to claim 2, wherein the header on the packet transmissionselects a sequence length from a plurality of resource blocks.
 5. Themethod according to claim 1, wherein the uplink resource informationincludes at least one of: a channel quality indicator, a pre-codingmatrix index, or a rank.
 6. The method according to claim 1, wherein theinitial access information request includes at least one of: a bandwidthrequest, a continuation of service request, or allocation of are-configured header.
 7. The method according to claim 1, wherein theresource request for sending uplink resource information is encoded withother uplink control data.
 8. A system for providing uplink control in awireless communication network, the system comprising: a mobileterminal, comprising: a processing element; a storage medium, coupled tothe processing element; and at least one antenna, coupled to theprocessing element; wherein the storage medium stores programinstructions executable by the processing element to: select a reservedrandom access signaling identification in response to receiving acommunication from a base station over an orthogonal frequency divisionmultiplexed (OFDM) wireless network; transmit to the base station aresource request determined at least in part based on the selectedreserved random access signaling identification; transmit an initialaccess information request to the base station to configure a basestation connection; retransmit a resource request to the base station toreceive for sending uplink resource information; transmit to the basestation a resource request for sending uplink resource information; andtransmit a service renewal request to the base station when the mobileterminal moves to a different cell.
 9. The system according to claim 8,wherein to select the reserved random access signaling identification,the program instructions are executable by the processing element toembed a header on a packet transmission communicated from the mobileterminal to the base station.
 10. The system according to claim 9,wherein the header on the packet transmission selects a sequence lengthfrom a single resource block.
 11. The system according to claim 9,wherein the header on the packet transmission selects a sequence lengthfrom a plurality of resource blocks.
 12. The system according to claim8, wherein the uplink resource information includes at least one of: achannel quality indicator, a pre-coding matrix index, or a rank.
 13. Thesystem according to claim 8, wherein the initial access informationrequest includes at least one of: a bandwidth request, a continuation ofservice request, or allocation of a re-configured header.
 14. The systemaccording to claim 8, wherein the resource request for sending uplinkresource information is encoded with other uplink control data.
 15. Anon-transitory computer readable storage medium that stores programinstructions executable by a processing element of a mobile terminal toperform: selecting a reserved random access signaling identification inresponse to receiving a communication from a base station over anorthogonal frequency division multiplexed (OFDM) wireless network;transmitting to the base station a resource request determined at leastin part based on the selected reserved random access signalingidentification; transmitting to the base station an initial accessinformation request to configure a base station connection; transmittinga resource request to the base station for sending uplink resourceinformation; receiving an initial access information request to the basestation from the mobile terminal to configure a base station connection;and transmitting a service renewal request to the base station when themobile terminal moves to a different cell.
 16. The non-transitorycomputer readable storage medium according to claim 15, wherein saidselecting the reserved random access signaling identification includesembedding a header on a packet transmission communicated from the mobileterminal to the base station, and wherein the header on the packettransmission selects a sequence length from a single resource block. 17.The non-transitory computer readable storage medium according to claim15, wherein said selecting the reserved random access signalingidentification includes embedding a header on a packet transmissioncommunicated from the mobile terminal to the base station, and whereinthe header on the packet transmission selects a sequence length from aplurality of resource blocks.
 18. The non-transitory computer readablestorage medium according to claim 15, wherein the uplink resourceinformation includes at least one of: a channel quality indicator, apre-coding matrix index, or a rank.
 19. The non-transitory computerreadable storage medium according to claim 15, wherein the initialaccess information request includes at least one of: a bandwidthrequest, a continuation of service request, or allocation of are-configured header.
 20. The non-transitory computer readable storagemedium according to claim 15, wherein the resource request is encodedwith other uplink control data.